It's the worst kept secret in Hollywood – but finally Twilight vampire Robert Pattinson has admitted that he and his sultry co-star Kristen Stewart are an item, RadarOnline.com can report.

The actors - who have been dating on the down-low since last year – were supposed to make their first public appearance at the UK's BAFTA Film awards on Sunday night, but opted to go separately at the last minute.

Rob, 23, was seen proudly cheering when Stewart, 19, accepted the BAFTA Rising Star award at the star-studded ceremony in London's Royal Opera House.

And later he admitted to the UK's Sun newspaper that the famous pair were indeed a couple.He told The Sun: “It is extremely difficult but we are together, yes.

“We can't arrive at the same time because of the fans. It goes crazy. This was supposed to be a public appearance as a couple but it's impossible. We are here together and it's a public event but it's not easy.

“We have to do all this stuff to avoid attention.”

After the BAFTAs, the couple headed to the Grosvenor House Hotel for the after-party, where they were spotted leaving at a relatively-respectable midnight.

But despite Rob's admission the young couple is keen to keep their romance low-profile, Stewart attended the Elle Awards alone Monday night while Pattinson was busy working on his new film Bel Ami